Timelines, centuries and millenniums

A timeline is a handy tool for marking events: it shows dates and events in order, over any period. It is a bit like the friend who meets you when you come back to school after three days off and tells you everything that happened, one thing after another. The book's timeline runs from the beginning of humanity to today, with a few important landmarks.

Part of the book's timeline is drawn as a dotted line: that marks a stretch that has been skipped, because otherwise the timeline would have to be almost 3 metres long! The dotted line honestly admits the drawing is not to scale.

A timeline also shows the order in which things happened. Even without reading the dates, you can see that the birth of the Buddha comes before the birth of Jesus.

Besides a year and a decade (10 years, such as 2001 to 2010), we use longer measures of time:

• A century is any period of 100 years. In history, centuries are counted every 100 years starting from the year 1 CE. So we are now in the 21st century CE, which runs from 2001 to 2100.
• Centuries BCE are counted from 1 BCE going back in time. So the 3rd century BCE covers the years 300 BCE to 201 BCE.
• A millennium is any period of 1,000 years. We are in the 3rd millennium CE, which began in 2001 CE and runs to 3000 CE. The 1st millennium BCE covers 1 BCE to 1000 BCE. (Both 'millenniums' and 'millennia' are correct.)

Many Indian calendars use the positions of the Sun and the Moon to set the months, such as Vaishākh, Māgh, Phālgun and Sāvan. A pañchānga is a book of tables listing the days of each month along with astronomical information. It can predict solar and lunar eclipses and the times of sunrise and sunset exactly. Pañchāngas are still widely used in India, and often also give weather predictions for the year and the dates and timings of festivals.